if statement, going back and forth-CodePudding

i am new to python, but have programmed some structured text, and a tiny bit c now i am working on a problem using if statements and it doesnt seem to work the way i am used to

example code:

more_guests = 0
loop = bool; loop = False
ferdig = int; ferdig = 1
while loop == False:
    guests = []
    more_guests = 0
    if int(ferdig) == 1:
        guest = input("type in guest ")
        more_guests = int(input("done? 1 for yes 2 for no "))
        if int(more_guests) == 1:
          guests.append(guest)
          ferdig == 3
        elif int(more_guests) == 2:
            guests.append(guest)
            ferdig == 2
        else:
            print("unvalid answer, please use 1 or 2")
            ferdig == 1
    elif int(ferdig) == 2:
        ferdig = 1
    elif int(ferdig) == 3:
        print(guests)
    else:
        loop = True

ive tried making sure its an integer and so on, just keep getting stuck on done? 1 for yes 2 for no, it always loop me back to type in guest

while using structured text i often used this way of going back and forth, but i cant seem to understand it in python, maybe i should rather use case/switch? anyways if anyone could help me understand if you can use the IF statement this way in python is highly appreciated

CodePudding user response：

Here is another option to accomplish what you are trying to do using functions.

guests = []

def add_guest():

    guest = input("type in guest ")
    guests.append(guest)
    add_more()

def add_more():

    more_guests = int(input("done? 1 for yes 2 for no ")) 

    #if they answer 1 we print out the final list
    if more_guests == 1: 
        print("the guest list is {}".format(guests))
        print('have a nice day')  

    #if they answer 2 we go to the add_guest function    
    elif more_guests == 2:  
        add_guest()

    #if they answer anything other than 1 or 2 we re-call the add_more function.  
    else: 
        print("unvalid answer, please use 1 or 2") 
        add_more()

add_guest()

CodePudding user response：

I think you wrote wrong operator. ferdig == 1 just comparing value operator. So it's return true(1) or false(0).

if you wnat to change the ferdig's value you should write ferdig = 3 in if statement.

CodePudding user response：

I've cleaned up your code a bit to get what I think you want.

guests = []
while True:
    guest = input("type in guest ")
    guests.append(guest)
    response = int(input("done? 1 for yes 2 for no "))
    if response == 1:
        print(guests)
        break
    elif response == 2:
        continue
    elif response == 3:
        print(guests)
    else:
        print("invalid answer, please use 1 or 2")

CodePudding user response：

Your code has a bunch of issues, here those have been fixed:

more_guests = 0
# you don't need to declare types, but if you want to, this is how
loop: bool = False
# however, Python can just infer the type itself like this
ferdig = 1
# you don't want to reset guests every time around the loop
guests = []
while loop == False:
    more_guests = 0
    if int(ferdig) == 1:
        guest = input("type in guest ")
        # you always want to append a guest, including if someone types a 1 after
        guests.append(guest)
        more_guests = int(input("done? 1 for yes 2 for no "))
        if int(more_guests) == 1:
            ferdig = 3
        elif int(more_guests) == 2:
            ferdig = 2
        else:
            print("invalid answer, please use 1 or 2")
            ferdig = 1
    elif int(ferdig) == 2:
        ferdig = 1
    elif int(ferdig) == 3:
        # after printing, you're done, you don't want to print forever
        print(guests)
        loop = True

Note that most of your code isn't really needed though, you're doing a lot of book-keeping that Python can do for you, or that's just not needed:

# this isn't needed, because you set that at the start of the loop anyway
# more_guests = 0
# this isn't needed, because you can tell when to stop from ferdig
# loop: bool = False
# starting at 2, since that means you want to keep going
ferdig = 2
guests = []
while ferdig != 1:
    # this isn't needed, you can just read ferdig
    # more_guests = 0
    # this isn't needed, you want a new guest on every loop
    #if int(ferdig) == 1:
    guest = input("type in guest ")
    guests.append(guest)
    ferdig = int(input("done? 1 for yes 2 for no "))
    # none of this is needed, all you need to know is if ferdig is 1 or 2
    # if int(more_guests) == 1:
    #     ferdig = 3
    # elif int(more_guests) == 2:
    #     ferdig = 2
    # else:
    if ferdig not in (1, 2):
        print("invalid answer, please use 1 or 2")
        ferdig = 1
    # this is also not needed, at this point ferdig will be 1 or 2
    # elif int(ferdig) == 2:
    #     ferdig = 1
    # elif int(ferdig) == 3:
# put the print outside the loop and it only prints once
print(guests)
# got rid of this
# loop = True

So, that's just:

ferdig = 2
guests = []
while ferdig != 1:
    guest = input("type in guest ")
    guests.append(guest)
    ferdig = int(input("done? 1 for yes 2 for no "))
    if ferdig not in (1, 2):
        print("invalid answer, please use 1 or 2")
        ferdig = 1
print(guests)

In the end, this would do the same:

more_guests = True
guests = []
while more_guests:
    guests.append(input("type in guest "))
    more_guests = input("done? 1 for yes") != '1'
print(guests)